Air handling systems, such as heating, ventilation, and air conditioning (HVAC) systems, are ubiquitous in modern building infrastructure. It is often necessary to monitor air that flows through such air handling systems for the presence of impurities that may pose a threat to the health and well-being of a building's occupants. For example, it is common to monitor the levels of oxygen, carbon monoxide, particulate, and smoke in the air that flows through a building's air handling system. Such monitoring is typically facilitated by so-called “duct detectors” that are installed at various locations throughout a building's ductwork.
Unlike conventional smoke detectors and other point detectors that are commonly mounted to ceilings or walls within a building and that function by passively sensing convection currents of ambient gas, a duct detector includes a detector assembly encased in a sealed housing mounted to the exterior of a duct. An inlet conduit that is in fluid communication with the interior of the detector housing extends into the duct to gather a sample of air flowing therethrough. The gathered air enters the detector housing, passes through a filter screen that catches large particulate, flows through the detector assembly, and exits the detector housing through an exhaust conduit. In other duct detector embodiments, the detector housing, inlet conduit, and exhaust conduit are omitted, and the detector assembly is mounted within a duct, directly in the path of air flowing therethrough. In either case, the duct detector continuously samples and analyzes air that flows through a duct. If certain properties of the sampled air exceed or fall below predetermined limits, the duct detector may activate an alarm, and/or may deactivate blowers that drive air through the air handling system to mitigate the further spread of unsuitable air throughout a building.
As will be appreciated, performance of such duct detectors can degrade over time due to, for example, the clogging of the detector assembly filter screen by accumulated particulate. As such, governmental agencies often require that duct detectors be periodically tested to demonstrate proper functionality. Such testing is typically performed manually by a technician or other individual using an airflow meter or a pressure-differential meter to measure airflow through a detector hosing (in the case of an externally-mounted duct detector) or through a duct (in the case of an internally-mounted duct detector).
A problem commonly associated with the manual testing of airflow in duct detectors is that duct detectors are often installed in elevated locations, sometimes above ceilings, with few surrounding structures capable of supporting the weight of an individual during testing. Detectors that are located in such areas offer poor accessibility, rendering the task of airflow testing highly inconvenient and even hazardous. Moreover, while conventional manual testing techniques are capable of measuring the amount of air flowing through a duct detector housing (in the case of an externally mounted duct detector) or through a duct at a location adjacent a detector assembly (in the case of an internally mounted duct detector), such measurements may not be indicative of the amount of air that flows through the detector assembly itself. For example, a manually-administered airflow test may indicate that an acceptable amount of air is flowing through a detector housing even if the filter screen of the detector assembly within the housing has become excessively clogged with particulate that prevents a sufficient amount of air from flowing through the detector assembly.